Thèse de doctorat : Sciences de l'univers et de l'environnement : Paris 12 : 2007. / Titre provenant de l'écran-titre. Bibliogr. : 265 réf.

As lagoas facultativas mantêm uma biota característica, decorrente de sua área superficial, que permite grande disponibilidade de energia luminosa para a coluna de água e promove o estabelecimento da comunidade fitoplanctônica. A presença dos nutrientes na forma assimilável aos microorganismos autotróficos induz a síntese de biomassa, a qual provoca a supersaturação de oxigênio dissolvido, que se constitui como substrato necessário ao desenvolvimento de bactérias heterotróficas, responsáveis pela degradação aeróbia da matéria orgânica nas camadas superiores da lagoa. Este estudo teve como objetivo principal a caracterização da estrutura da comunidade fitoplanctônica em termo de diversidade de espécies, densidade abundância relativa e dominância na lagoa facultativa do módulo III da estação de tratamento de esgotos de mangabeira, na cidade de João Pessoa - PB. As amostragens foram realizadas em escala semanal e sazonal, com coletas entre 8 e 9 horas da manhã, no período de junho/2008 a fevereiro/2009, as regiões afluente e efluente. As alterações no comportamento sazonal das variáveis físicas, químicas e biológicas, assim como das climatológicas, foram analisadas através da ferramenta estatística multivariada da Análise de Componentes Principais (ACP). Foram identificados 36 taxa nas duas regiões de amostragem e apenas cianobactérias foram predominantes durante o período deste estudo. Contudo, não foi observada variação sazonal na composição da comunidade fitoplanctônica nas duas regiões de amostragem. Embora, algumas espécies foram mais frequentes na região afluente, a densidade total apresentou nítida variação sazonal, com valores entre 2,0 x \'10 POT.4\' e 1,2 x \'10 POT.5\' ind/mL. A cianobactéria Planktothrix agardhii, a qual pode produzir a hepatotoxina microcistina, foi a espécie que mais contribuiu para a densidade, assim como para o biovolume. / Facultative ponds keep a characteristic biota, as a result of its superficial area, wich permits high availability of solar energy to the water column favoring the establishment of the phytoplanktonik community. The presence of available nutrients to the autotrophic microorganisms leads to the synthesis of biomass cellular into the pond and it causes the oversaturation dissolved oxygen, which is necessary to the development of heterotrophic bacteria, responsible for aerobic stabilization of organic material at the upper layer of the pond. The main goal of this study was to caracterize the structure of phytoplanktonic community in relation to different species, biomass, relative abundance and dominance at the facultative pond of the module III of waste water plants of Mangabeira (João Pessoa - PB). Samples were taken in seasonal and weekly scale, with collects between 8 a.m to 9 a.m, in the period of June, 2008 to February, 2009, at the regions of inflow and outflow of effluents. Alterations in seasonal behavior of the physical, chemical and biological variables, as well as climatic, were analyzed through statistics multivariate tool of the principal component of analysis (PCA). It was identified 36 taxa on the facultative pond and only the cyanobacteria were predominant during the period of this study. However, it was not observed temporal variation in the composition of phytoplanktonic community at two collected regions. Although, it was noticed that some species were more frequent at the region of inflow than at the outflow. It was also observed that the high total phytoplanktonic density shows a clear seasonal variation, with values between 2.0 x \'10 POT.4\' and 1,2 x \'10 POT.5\' ind/mL. The cyanobacteria Planktothrix agardhii, which may produce hepatotoxic microcystins, was the species that more contributed for the density as well as the biovolume.

En dépit de la ré-oligotrophisation de nombreux lacs d'Europe du nord au cours des deux dernières décennies, les développements massifs de cyanobactéries toxiques, telle que Planktothrix rubescens, adaptée aux écosystèmes mésotrophes, sont encore largement observés. Parmi les cyanotoxines produites par cette espèce, les microcystines (MCs) sont les toxines les plus fréquemment rencontrées et sont reconnues comme des molécules perturbatrices de tous les compartiments trophiques des écosystèmes lacustres. Ces blooms toxiques affectent notamment les lacs péri-alpins pour lesquels des risques de contaminations des populations piscicoles exploitées ont été démontrés. Cependant, il existe encore un manque de connaissances important tant concernant les voies de transfert de ces toxines au sein des réseaux trophiques limniques, que leurs effets physiologiques sur les populations de poisson. Dans le cadre de ce travail de thèse, deux modèles de poissons, dont les répartitions spatiales verticales diffèrent (juvéniles de perche et corégones), ont été considérés. Les objectifs principaux ont été traités d'une part au travers d'une approche expérimentale (par gavage) visant à analyser les processus d'accumulation et de détoxification, ainsi que les effets génotoxiques des MCs sur ces deux espèces modèles. Les réponses physiologiques ainsi étudiées ont permis de mettre en évidence que les juvéniles de perche et les corégones sont capables de détoxifier une partie des MCs ingérées, mais cependant des effets génotoxiques sont observés suite à l'exposition des poissons aux MCs. D'autre part, des approches écosystémiques ont permis (1) d'explorer les effets potentiels de la présence du bloom sur la répartition spatiale des poissons (2) d'évaluer les niveaux de contaminations par les MCs pour les deux espèces de poisson en tenant compte de la variabilité saisonnière (3) d'identifier les principaux vecteurs zooplanctoniques de MCs jusqu'aux poissons. Les résultats acquis montrent que les filaments de P. rubescens constituent une ressource alimentaire en période de bloom pour les organismes zooplanctoniques brouteurs et qu'un transfert de MCs est possible jusqu'aux espèces zooplanctoniques prédatrices et in fine jusqu'aux poissons. Nos résultats mettent également en avant que les voies de contaminations ainsi que les intensités de contamination des poissons peuvent varier aussi bien à l'échelle saisonnière que journalière. Ces variations sont expliquées à la fois par les changements de régime alimentaire des poissons, les variations journalières de la production de MCs par P. rubescens, et les abondances et distributions verticales des différentes proies zooplanctoniques. A l'issue de ce travail, la part importante du transfert trophique des MCs jusqu'aux poissons a été vérifiée dans les cas des contaminations chroniques qui caractérisent les conditions de blooms des lacs péri-alpins (concentrations en cyanobactéries et en toxines modérées à fortes au cours de plusieurs mois). / Many deep peri-alpine lakes which are currently under re-oligotrophication are impacted by Planktothrix rubescens blooms. Among cyanotoxins produced by P. rubescens, microcystins (MCs) are the most commonly studied and are involved in many ecological disturbances. In peri-alpine lakes, these blooms might affect exploited fish species due to toxin contaminations. However, there is still a lack of knowledge regarding both transfer pathways of the toxin and their physiological effects on fish populations. In this work, two models of fish populations were considered (Young-Of-Year (YOY) perch and whitefish which exhibit distinct vertical distributions). The main objectives were on the one hand investigated through an experimental approach to analyze on the two model species, accumulation and detoxification processes as well as genotoxic effects of MCs. From these experiments, we showed that YOY perch and whitefish were able to detoxify part of the MCs but that genotoxic effects were still observed. On the other hand, ecosystemic approaches allowed (1) to explore the potential effects of the presence of bloom on the spatial distribution of fish, (2) to assess the levels of contamination by MCs for both fish species taking into account the seasonal variability, (3) to identify the main zooplanktonic vectors of MCs to fish. Our results revealed that the filaments of P. rubescens are a food resource for zooplankton grazers, and that a trophic transfer of MCs exists from herbivorous to their zooplanktonic predators and in fine to fish. Our results also highlight that the contamination pathways and their intensities could vary both at seasonal and daily scales. These variations are explained by both changes in fish diet, daily variations in the production of MCs by P. rubescens, and abundances and vertical distributions of zooplanktonic preys. Overall, we highlighted the importance of MCs trophic transfer in fish intoxication in the case of chronic contaminations observed in peri-alpine lakes (moderate to severe cyanobacteria/toxins concentrations over several months).

As lagoas facultativas mantêm uma biota característica, decorrente de sua área superficial, que permite grande disponibilidade de energia luminosa para a coluna de água e promove o estabelecimento da comunidade fitoplanctônica. A presença dos nutrientes na forma assimilável aos microorganismos autotróficos induz a síntese de biomassa, a qual provoca a supersaturação de oxigênio dissolvido, que se constitui como substrato necessário ao desenvolvimento de bactérias heterotróficas, responsáveis pela degradação aeróbia da matéria orgânica nas camadas superiores da lagoa. Este estudo teve como objetivo principal a caracterização da estrutura da comunidade fitoplanctônica em termo de diversidade de espécies, densidade abundância relativa e dominância na lagoa facultativa do módulo III da estação de tratamento de esgotos de mangabeira, na cidade de João Pessoa - PB. As amostragens foram realizadas em escala semanal e sazonal, com coletas entre 8 e 9 horas da manhã, no período de junho/2008 a fevereiro/2009, as regiões afluente e efluente. As alterações no comportamento sazonal das variáveis físicas, químicas e biológicas, assim como das climatológicas, foram analisadas através da ferramenta estatística multivariada da Análise de Componentes Principais (ACP). Foram identificados 36 taxa nas duas regiões de amostragem e apenas cianobactérias foram predominantes durante o período deste estudo. Contudo, não foi observada variação sazonal na composição da comunidade fitoplanctônica nas duas regiões de amostragem. Embora, algumas espécies foram mais frequentes na região afluente, a densidade total apresentou nítida variação sazonal, com valores entre 2,0 x \'10 POT.4\' e 1,2 x \'10 POT.5\' ind/mL. A cianobactéria Planktothrix agardhii, a qual pode produzir a hepatotoxina microcistina, foi a espécie que mais contribuiu para a densidade, assim como para o biovolume. / Facultative ponds keep a characteristic biota, as a result of its superficial area, wich permits high availability of solar energy to the water column favoring the establishment of the phytoplanktonik community. The presence of available nutrients to the autotrophic microorganisms leads to the synthesis of biomass cellular into the pond and it causes the oversaturation dissolved oxygen, which is necessary to the development of heterotrophic bacteria, responsible for aerobic stabilization of organic material at the upper layer of the pond. The main goal of this study was to caracterize the structure of phytoplanktonic community in relation to different species, biomass, relative abundance and dominance at the facultative pond of the module III of waste water plants of Mangabeira (João Pessoa - PB). Samples were taken in seasonal and weekly scale, with collects between 8 a.m to 9 a.m, in the period of June, 2008 to February, 2009, at the regions of inflow and outflow of effluents. Alterations in seasonal behavior of the physical, chemical and biological variables, as well as climatic, were analyzed through statistics multivariate tool of the principal component of analysis (PCA). It was identified 36 taxa on the facultative pond and only the cyanobacteria were predominant during the period of this study. However, it was not observed temporal variation in the composition of phytoplanktonic community at two collected regions. Although, it was noticed that some species were more frequent at the region of inflow than at the outflow. It was also observed that the high total phytoplanktonic density shows a clear seasonal variation, with values between 2.0 x \'10 POT.4\' and 1,2 x \'10 POT.5\' ind/mL. The cyanobacteria Planktothrix agardhii, which may produce hepatotoxic microcystins, was the species that more contributed for the density as well as the biovolume.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / No semi-Ãrido brasileiro, devido Ãs caracterÃsticas climÃticas, ao regime irregular de chuvas e Ãs caracterÃsticas do solo, a principal fonte de Ãgua para abastecimento humano tem sido os reservatÃrios artificiais de superfÃcie, aÃudes. A ocupaÃÃo e exploraÃÃo desordenada dos recursos naturais nas bacias hidrogrÃficas, alÃm da alta evaporaÃÃo e da radiaÃÃo solar, interferem negativamente na qualidade da Ãgua armazenada. Como consequÃncia, esses reservatÃrios apresentam um processo de eutrofizaÃÃo acelerado, levando frequentemente a floraÃÃes de fitoplÃnctons, comunidade esta predominantemente dominada por CianobactÃrias. Devido grande parte desses organismos serem produtores de toxinas, podendo causar uma sÃrie de problemas à populaÃÃo, decidiu-se monitorar a comunidade fitoplanctÃnica do aÃude SÃtios Novos, reservatÃrio de usos mÃltiplos, localizado no municÃpio de Caucaia-CE, de janeiro de 2010 a junho de 2011 investigando a produÃÃo de toxinas pelos organismos dominantes. Identificou-se 41 tÃxons, 19 de cianobactÃrias e 22 de algas. Apesar da predominÃncia de nÃmero de tÃxons de algas, estas representaram menos de 10% dos organismos quantificados, com exceÃÃo de 1 amostragem. Jà as cianobactÃrias estiveram presentes em todas as amostragens, dominando quantitativamente o ambiente aquÃtico. Dentre o grupo de cianobactÃrias, destacaram-se Planktothrix agardhii (PA) e Cylindrospermosis raciborskii (CR). A abundÃncia de PA ao longo de todo o perÃodo de amostragem variou de 0 a 5.83x105 cel.mL-1, o que representou 94% da abundÃncia total do fitoplÃncton. A densidade mÃdia da PA foi 7.54.104 cel.mL-1. A abundÃncia CR no mesmo perÃodo variou de 0 a 3.32x104 cell.mL-1, representando 18,9% do total da comunidade fitoplanctÃnica. A abundÃncia mÃdia de CR foi 8.21.103 cel.mL-1. As espÃcies dominantes foram isoladas, e realizando-se bioensaios em camundongos, teste ELISA e mÃtodo de detecÃÃo por HPLC, observou-se a produÃÃo de STX e dc-STX pela CR e dc-GTX pela PA. Essa problemÃtica evidencia a necessidade da implementaÃÃo de aÃÃes integradas dos ÃrgÃos ambiental, de gestÃo dos recursos hÃdricos e companhia de sanamento estadual visando a prevenÃÃo e remediaÃÃo do processo de degradaÃÃo da qualidade da Ãgua, atuando na ampliaÃÃo do saneamento bÃsico, na educaÃÃo ambiental, na fiscalizaÃÃo dos usos e ocupaÃÃes do solo na bacia hidrogrÃfica mas, principalmente, no controle das atividades de piscicultura na bacia hidrÃulica, que ocorrem de maneira superintensiva. / In Brazilian semi-arid Northeast region due to irregular rainfall regime, climatic and soil characteristics, the main source of human water supply has been artificial surface reservoirs. Disorderly occupation and exploitation of natural resources on those hydrographic basins, alongside high evaporation and solar radiation, promote negative impact on stored water quality. As a consequence, the reservoirs present themselves in a process of accelerated eutrophication, often leading to phytoplankton blooms, predominantly dominated by Cyanobacteria. Due to many of these organisms are toxin-producing, which can cause a sort of problems to the population, it was decided to monitor the phytoplankton community of a multipurpose reservoir, located in the municipality of Caucaia-CE, from January 2010 to June 2011, as well as investigate the production of toxins by the dominant organisms. We identified 41 taxa, 19 of cyanobacteria and 22 of algae. Despite the predominance of algae over the identified taxa, they accounted for less than 10% of the quantified organisms, except for one sample. However cyanobacteria were present in all samples, quantitatively dominating the aquatic environment. Among the group of cyanobacteria, excelled Planktothrix agardhii (PA) and Cylindrospermosis raciborskii (CR). PA abundance along all sampling period ranged from 0 to 5.83x105 cells.mL-1 , which accounted for 94% of the total phytoplankton abundance. The average density of PA was 7.54.104 cells.mL-1 . The CR abundance in the same period ranged from 0 to 3.32x104 cells.mL-1 , accounting for 18,9% of total phytoplankton community. The average abundance of CR was 8.21.103 cells.mL-1. The dominant species were isolated and carrying out mice bioassay , ELISA and HPLC analysis, we observed the production of STX and dc-STX by CR and dc-GTX by PA. This issue highlights the need for the implementation of integrated actions from environmental agencies, water resources management and sanitation State companies towards the prevention and remediation of the degradation of water quality, acting in the expansion of sanitation, environmental education, oversighting of the use and occupation of the watershed lands, but mainly in the control of aquaculture activities in the hydraulic basin, which occur in a super intensive way.

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La recherche a été initiée par l'observation d'efflorescences de Planktothrix agardhii, une cyanobactérie dulçaquicole potentiellement toxique, dans deux étangs saumâtres, les étangs de l'Olivier et de Bolmon, avec dans ce dernier le déclin de l'espèce concomitamment à une augmentation de salinité. L'objectif de l'étude consistait à évaluer l'influence de la salinité du milieu sur la performance, l'hégémonie et la production de toxine de Planktothrix agardhii au sein de la communauté phytoplanctonique.La réalisation de suivis pluriannuels in situ couplés à des expérimentations en milieu contrôlé a permis de démontrer (i) la capacité d'acclimatation et d'adaptation à la salinité de Planktothrix agardhii, laquelle garantit sa suprématie et sa production toxinique en milieu saumâtre ; et (ii) la modification structurale et fonctionnelle de la communauté phytoplanctonique suite à une augmentation de salinité supérieure au seuil d'halotolérance de Planktothrix agardhii. La recherche témoigne ainsi de la versatilité des cyanobactéries qui renforce leur aptitude à être de bons compétiteurs, laissant présager leur persistance, la continuité de leurs nuisances, et leur expansion dans le futur. / The research was launched by the observation of Planktothrix agardhii blooms, a potentially toxic freshwater cyanobacterium, in two brackish ponds, the Olivier and Bolmon ponds, with in the latter, the concomitantly collapse of P. agardhii with an increase in salinity. The goal of the study was to assess the salinity influence on the performance, the dominance and the toxin production of P. agardhii within the phytoplankton community.The achievement of a long-term monitoring in situ combined with batch cultures experiments has demonstrated (i) the ability of P. agardhii to acclimate and adapt to salinity, which ensure its supremacy and its toxin production in brackish areas, and (ii) the structural and functional changes of the phytoplankton community with the exceeding of the salt-tolerance threshold of P. agardhii .The research reflects the cyanobacteria versatility that enhances their suitability for being good performers, suggesting their persistence along with their nuisances, and their expansion in the future.

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No description available.